This invention relates to new and improved apparatus for transferring markings from a floor to a ceiling location in true vertical. In building construction and repair, it is frequently necessary to locate and mark a spot on a ceiling or overhead structure in accordance with a designer's plans for accurate location and installation of walls, electrical outlets, lighting fixtures, heating, ventilating or air conditioning ducts or the like.
Conventionally, workman lay out the location of such markings on the floor for ease and accuracy of measurement. Transferrance of these markings accurately to the ceiling or overhead has previously been costly and time consuming. By one technique, usually requiring two men, a conventional plumb bob is used to determine the ceiling spot location. Such a technique often requires an inordinate amount of time for the plumb bob to come to rest and accuracy may be poor when the wind interferes with the operation. Some prior art systems have used a light source (usually incoherent) and lens system to project a spot of light on to the overhead from the source accurately located on the floor. However, because several separate parts are needed to make up and mount the lens projection system, such a device is susceptible to the misalignment and inaccuracies resulting from even the normal and expected bumps and jolts encountered in use of the device in a construction environment. Similar devices using the coherent light of a laser beam to permit omission of the lens system still are subject to misalignment between the floor marking "pointer" and laser which is usually mounted some distance above the "pointer".
In the present invention, a "double-beam" laser is used. In such lasers, which are commercially available, light beams are emitted from both ends of the lasing element. In order to provide the properly aligned internal light reflections required for laser action, the partially reflective end walls of the laser element are required to be parallel to an extreme degree of accuracy. Thus, when the laser is operating, the light beams emitted are known to be aligned exactly 180 degrees opposite each other. Therefore, when one beam is directed to illuminate a floor marking from directly above, the other beam illuminates a spot on the overhead exactly vertical from the floor marking. By the alignment system of the present invention then at least one major source of inaccuracy of alignment has been eliminated.
It is a principal object of the present invention to provide a device to reduce the time and labor required to transfer location markings from one surface to another.
It is a further object to provide a device for the transfer of location markings from one surface to another with improved accuracy.
It is a still further object to provide a lightweight portable inexpensive tool useful for the transfer of location markings.
It is an even further object to provide a tool for the transfer of location markings which is simple, easy to operate and does not require special training or skill of the user.
An additional object is to provide a tool for the transfer of location markings which is rugged and not readily subject to damage or misalignment from ordinary on-the-job handling treatment.